1. Field of the Invention
The present invention relates to an image processing method and an image processing apparatus for calculating motion vectors for a plurality of images, and a program that performs the image processing method.
2. Description of the Related Art
A technique for calculating motion vectors for the frames of moving pictures, and aligning the frames based on the motion vectors has been disclosed. Further, a technique for calculating motion vectors at feature points representing the feature of an image, and reflecting the motion vectors onto the individual pixels of the image, has been proposed as a method for calculating motion vectors for the individual pixels that are included in an image. Furthermore, in Japanese Patent No. 3935500, a technique is described whereby color differences, among a plurality of feature points that are included in a single image, or differences of motion vectors that are temporarily obtained for the individual feature points, are regarded as degrees of correlation for the feature points, and motion vector smoothing is performed using the degrees of correlation to obtain motion vectors, for the feature points, that are to be employed to perform the alignment of frames.
According to the technique disclosed in Japanese Patent No. 3935500, the degrees of correlation for a plurality of feature points included in a specific image affect the calculation of motion vectors; however, an area that has feature points similar to those of the specific image is not always included in an image other than the specific image. There is a case wherein the points that correspond to the feature points of a reference image are absent in a comparison image, e.g., before taking a photograph to obtain the comparison image, the camera was moved, and as a result, an object in the reference image disappears in the comparison image; or a case wherein a targeted object is rotated and points corresponding to the feature points of the reference image are hidden in the comparison image. As a result, when frame synthesis is performed for frames for which images differ greatly, feature points will be detected for which motion vectors can not be defined. Therefore, when the technique described in Japanese Patent No. 3935500 is employed to effect a correlation at the feature points for the specific image to the calculation of motion vectors, the precision with which motion estimation is performed may be degraded.
While taking the above problem into account, one objective of the present invention is to provide an image processing method and an image processing apparatus for precisely determining motion vectors for the feature points of an image, and a program therefor.